Manufacturing method for magnetic tape cassette

Abstract

A method of manufacturing a magnetic tape cassette by using a molding die having a fixed part and a second part including a submarine gate and a plurality of movable cores. The method includes the steps of defining an initial opening in the molding die between the fixed part and the movable cores, filling a molten plastic for molding the body of the cassette into the initial opening in the molding die, selectively moving the plurality of cores to change the size of the initial opening to define a new opening connected to the submarine gate, and filling the new opening through the submarine gate with a molten plastic different from the plastic already filled into the initially formed opening in order to mold the body in a plurality of colors.

I claim: 
     
       1. A method of manufacturing a magnetic tape cassette, by using a molding die comprising a fixed part and a second part including a submarine gate and a plurality of movable cores, said method comprising the steps of; defining an initial cavity in said molding die between said fixed part and said moveable cores, said cavity having a specific size for forming a body of said cassette;   filling a molten plastic for molding said body of said cassette into said initial cavity in said molding die;   selectively moving said coles to define new cavities for at least two windows, said windows being separated by an intermediate portion of said cassette body and formed in the longitudinal direction thereof, said cavities being connected to said submarine gate; and   injecting a molten optically-transmissive plastic into said new cavities in the molding die through the submarine gate in a longitudinal direction along said intermediate portion already molded from the other plastic whereby pressure of said optically-transmissive plastic is lower than flow pressure of said other plastic; and   flow of said optically-transmissive plastic is in said longitudinal direction, so that deformation of said intermediate portion due to stress is prevented during said filling of said new cavities.   
     
     
       2. A method according to the claim 1, in which the plastic injected into the initial cavity in said molding die during said filling step is an optically-transmissive plastic and forms a peripheral portion of the body of the magnetic tape cassette; said plastic injected into said new cavities through the submarine gate is an optically-transmissive plastic different in optical transmissivity from the former; and each of the windows is made of a plurality of layers molded from said plastics. 
     
     
       3. The method according to claim 1 in which one of said window forming cores prevents any flow of said molten plastic between said fixed part and said window forming core during said filling of said initial cavity.